Transfer RNAs (tRNAs) contain a wide variety of posttranscriptional modifications that are important for accurate decoding. Mammalian mitochondrial tRNAs (mt-tRNAs) are modified by nuclear-encoded tRNA-modifying enzymes; however, the physiological roles of these modifications remain largely unknown. In this study, we report that Cdk5 regulatory subunit-associated protein 1 (Cdk5rap1) is responsible for 2-methylthio (ms(2)) modifications of mammalian mt-tRNAs for Ser(UCN), Phe, Tyr, and Trp codons. Deficiency in ms(2) modification markedly impaired mitochondrial protein synthesis, which resulted in respiratory defects in Cdk5rap1 knockout (KO) mice. The KO mice were highly susceptive to stress-induced mitochondrial remodeling and exhibited accelerated myopathy and cardiac dysfunction under stressed conditions. Furthermore, we demonstrate that the ms(2) modifications of mt-tRNAs were sensitive to oxidative stress and were reduced in patients with mitochondrial disease. These findings highlight the fundamental role of ms(2) modifications of mt-tRNAs in mitochondrial protein synthesis and their pathological consequences in mitochondrial disease.

Sarcopenia due to loss of skeletal muscle mass and strength leads to physical inactivity and decreased quality of life. The number of individuals with sarcopenia is rapidly increasing as the number of older people increases worldwide, making this condition a medical and social problem. Some patients with sarcopenia exhibit accumulation of peri-muscular adipose tissue (PMAT) as ectopic fat deposition surrounding atrophied muscle. However, an association of PMAT with muscle atrophy has not been demonstrated. Here, we show that PMAT is associated with muscle atrophy in aged mice and that atrophy severity increases in parallel with cumulative doses of PMAT. We observed severe muscle atrophy in two different obese model mice harboring significant PMAT relative to respective control non-obese mice. We also report that denervation-induced muscle atrophy was accelerated in non-obese young mice transplanted around skeletal muscle with obese adipose tissue relative to controls transplanted with non-obese adipose tissue. Notably, transplantation of obese adipose tissue into peri-muscular regions increased nuclear translocation of FoxO transcription factors and upregulated expression FoxO targets associated with proteolysis ( Atrogin1 and MuRF1 ) and cellular senescence ( p19 and p21 ) in muscle. Conversely, in obese mice, PMAT removal attenuated denervation-induced muscle atrophy and suppressed upregulation of genes related to proteolysis and cellular senescence in muscle. We conclude that PMAT accumulation accelerates age- and obesity-induced muscle atrophy by increasing proteolysis and cellular senescence in muscle.

Skeletal muscle atrophy, or sarcopenia, is commonly observed in older individuals and in those with chronic disease and is associated with decreased quality of life. There is recent medical and broad concern that sarcopenia is rapidly increasing worldwide as populations age. At present, strength training is the only effective intervention for preventing sarcopenia development, but it is not known how this exercise regimen counteracts this condition. Here, we report that expression of the inflammatory mediator angiopoietin-like protein 2 (ANGPTL2) increases in skeletal muscle of aging mice. Moreover, in addition to exhibiting increased inflammation and accumulation of reactive oxygen species (ROS), denervated atrophic skeletal muscles in a mouse model of denervation-induced muscle atrophy had increased ANGPTL2 expression. Interestingly, mice with a skeletal myocyte-specific knockout had attenuated inflammation and ROS accumulation in denervated skeletal muscle, accompanied by increased satellite cell activity and inhibition of muscular atrophy compared with mice harboring wildtype Moreover, consistent with these phenotypes, wildtype mice undergoing exercise training displayed decreased ANGPTL2 expression in skeletal muscle. In conclusion, ANGPTL2 up-regulation in skeletal myocytes accelerates muscle atrophy, and exercise-induced attenuation of ANGPTL2 expression in those tissues may partially explain how exercise training prevents sarcopenia.

BACKGROUND Genetic variants in the human CDKAL1 (CDK5 regulatory subunit associated protein 1–like 1) gene have been associated with reduced insulin secretion and type 2 diabetes (T2D). CDKAL1 is a methylthiotransferase that catalyzes 2-methylthio (ms2) modification of the adenine at position 37 (A37) of cytoplasmic tRNALys(UUU). We investigated the ms2-modification level of tRNALys(UUU) as a direct readout of CDKAL1 enzyme activity in human samples. METHOD We developed a quantitative PCR (qPCR)-based method to measure ms2 modification. tRNALys(UUU) was reverse-transcribed with 2 unique primers: Reverse primer r1 was designed to anneal to the middle of this tRNA, including the nucleotide at A37, and reverse primer r2 was designed to anneal to the region downstream (3′) of A37. Subsequent qPCR was performed to detect the corresponding transcribed cDNAs. RESULTS The efficiency of reverse transcription of tRNALys(UUU) was ms2-modification dependent. The relative difference in threshold cycle number obtained with the r1 or r2 primer yielded the ms2-modification level in tRNALys(UUU) precisely as predicted by an original mathematical model. The method was capable of measuring ms2-modification levels in tRNALys(UUU) in total RNA isolated from human peripheral blood samples, revealing that the ms2-modification rate in tRNALys(UUU) was decreased in individuals carrying the CDKAL1 genotype associated with T2D. In addition, the ms2-modification level was correlated with insulin secretion. CONCLUSIONS The results point to the critical role of ms2 modification in T2D and to a potential clinical use of a simple and high-throughput method for assessing T2D risk.

When cement-based materials are carbonated, some of their physicochemical properties are changed, which includes reductions of porosity by 20% and pH from 12-13 to 8-9. These changes can enhance the retention ability of cementitious solids containing hazard waste. This research studied the effect of carbonation on the leaching resistance of hazardous waste cement solidification. The finite element software COMSOL Multiphysics was used to simulate the process of accelerated carbonation and the effect of carbonation on leaching. Laboratory tests were conducted to validate the numerical models. Parametric studies from the numerical simulations revealed that carbonation could significantly improve leaching retention capabilities of cementitious solids containing hazardous wastes.

In recent years, interest in biological activities of compounds from marine organisms has intensified. Cancer is the most principal enemy for human life and health. For the first time, to the best of our knowledge, we investigated a novel algae-derived polysaccharide for its role in inducing apoptosis and cell cycle arrest in human gastric carcinoma MKN45 cells. We found that the novel polysaccharide suppressed MKN45 cell proliferation, induced cell apoptosis and arrested the cells at G2/M phase. Furthermore, we observed that the generation of reactive oxygen species (ROS) and the phosphorylation of Jun N-terminal kinase (JNK), p53, caspase-9 and -3 were induced in the polysaccharide-treated MKN45 cells. In addition, pretreatment with N-acetyl-cysteine (NAC) and SP600125, the inhibitor of ROS and JNK, induced MKN45 cell proliferation, prevented the cell apoptosis and released the cells from cycle arrest. Finally, we found that pretreatment with NAC prevented the JNK, p53, caspase-9 and -3 protein phosphorylation induced by the polysaccharide, however, pretreatment with SP600125 did not affect the generation of ROS, suggesting that ROS is upstream of JNK. Taken together, the novel polysaccharide induced cancer cell apoptosis and arrested cell cycle via ROS/JNK signaling pathway.

Diabetic retinopathy is a common complication of diabetes mellitus (DM). The oxidative damage inflicted on retinal pigment epithelial (RPE) cells by high glucose closely approximates the molecular basis for the loss of vision associated with this disease. We investigate a novel algae-derived polysaccharide compound for its role in protecting ARPE-19 cells from high glucose-induced oxidative damage. ARPE-19 cells were cultured for 4 d with normal concentration of D-glucose, and exposed to either normal or high concentrations of D-glucose in the presence or absence of the polysaccharide compound at variety of concentrations for another 48 h. Taurine was used as a positive control. Activity of super oxide dismutase (SOD) and concentration of glutathione (GSH) were measured as well as cytotoxicity of high glucose and the polysaccharide compound. To analyse cellular damage by high glucose, activation of Annexin V and p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) were examined. Our results showed that a significant cellular damage on ARPE-19 cells after 48 h treatment with high glucose, accompanied by a decrease in SOD activity and GSH concentration; high glucose also caused ARPE-19 cell apoptosis and activation of p38MAPK and ERK. As the non-toxic polysaccharide compound protected ARPE-19 cells from high glucose-induced cellular damage, the compound recovered SOD activity and concentration of GSH in the cells. The compound also abrogated the cell apoptosis and activation of p38MAPK and ERK. Therefore, the polysaccharide compound derived from algae extracts could be unique candidate for a new class of anti-DM and anti-oxidative damage.Key words polysaccharide compound; retinal pigment epithelium; superoxide dismutase; glutathione Diabetic retinopathy (DR) is a common complication of diabetes mellitus.1) The basis for the loss of vision associated with this disease closely approximates the oxidative damage inflicted on retinal pigment epithelial (RPE) cells by high glucose.2) Superoxide dismutase (SOD) is regarded as the major enzyme for protection against oxidative damage to RPE cells.3,4) Glutathione (GSH), a tripeptide present in RPE cells, also protects RPE cells from oxidative damage. 5) Therefore, to protect retina from oxidative damage, it is exceedingly important to protect RPE cells via maintaining appropriate concentrations of SOD and GSH and the enzymes as well.In the past, drugs used to ward against oxidative damage often produced a number of unwanted side-effects. 6) In recent years, interest in biological activities of compounds from marine organisms has intensified.7) Many such compounds have been investigated, and some have been developed into health food (herbal medicine) and made commercially available in Japan.8) Some of the similar compounds have already been investigated for their ability to improve human immunologic and hepatic functions, to induce interferon synthesis, to inhibit the replication of hepatitis B virus, and to anti-diabetic. These compou...

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